The vitality of bone tissues and their rapid growth in fetuses have been subjects of many investigations. However, bone transplantation in utero has never been accomplished in nonhuman primates. The allogeneic bone transplantation has been performed on twenty rhesus monkeys on 120-135 day of gestation and no allograft rejection was observed. Two techniques were applied. In the first the allograft (bone plug) of fetal humerus was transplanted from fetus (donor) to fetus (recipient). In the second allogeneic paste (small bone particle mixed with a tissue culture medium) was implanted in the same area of humeral midshaft as in the first technique. In both techniques no rejection of the allograft was noted. The fetal-maternal immunologic properties together with the inherent growth potential of the highly vascular fetal bone contribute to rapid healing and normal osteogenesis in the transplanted area. Thus, our results provide a feasibility for a new surgical basis for intrauterine corrective intervention in some congenital bone defects.